package me.timlong.Tree;

import java.util.Arrays;

public class BinaryTreeReconstruction {
    /**
     * 题干：
     * 输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。
     * 假设输入的前序遍历和中序遍历的结果中都不含重复的数字。
     * 例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，
     * 则重建二叉树并返回。
     *
     * 解决方案：
     * 递归  Arrays.CopyOfRange
     *
     * @param pre
     * @param in
     * @return
     */
    public TreeNode reConstructBinaryTree(int [] pre, int [] in) {

        if(0 == pre.length || 0 == in.length)
            return null;

        TreeNode root = new TreeNode(pre[0]);
        for(int i = 0; i < in.length; i++){
            if(root.val == in[i]) {
                root.left = reConstructBinaryTree(Arrays.copyOfRange(pre, 1, i + 1),
                        Arrays.copyOfRange(in, 0, i));

                root.right = reConstructBinaryTree(Arrays.copyOfRange(pre, i + 1, pre.length),
                        Arrays.copyOfRange(in, i + 1, in.length));
            }
        }

        return root;
    }


    public static void main(String[] args) {

        int[] pre = {1,2,4,7,3,5,6,8};
        int[] in = {4,7,2,1,5,3,8,6};

        TreeNode root = new BinaryTreeReconstruction().reConstructBinaryTree(pre, in);
        System.out.println(root.left.val);
        System.out.println(root.right.val);
        System.out.println(root.right.left.val);


    }
}

//   Definition for binary tree
class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}
